Thermal transitions and solidification kinetics of poly(lactic acid) and blends with epoxidized natural rubber

• Verification of the validity of Mahadevan plots for vitrification and devitrification transitions of PLA.
• Role of crystallinity in PLA in relation to vitrification and devitrification phenomena.
• Effect of miscibilized species derived from the rubbery component of the blend on the crystallization of PLA.

The reactivity of polylactic acid (PLA) with epoxidized natural rubber (ENR50) was confirmed by monitoring the changes in melt viscosity during mixing and by TGA runs.The plasticization resulting from a partial miscibilization of ENR50 during mixing was found to have opposite effects on the crystallization of the PLA matrix, depending on the temperature scanning mode. An increase in heat of crystallization (ΔHc) with increasing temperature scanning rate was observed when heated from the glassy state, while a corresponding reduction in ΔHc was obtained in cooling scans from the melt.Studies on the kinetics of events have shown that the classical Kissinger plots for crystallization by heating from the glassy state display a variable activation energy for the case of the reactive blend. The vitrification kinetics, on the other hand, could be modelled quite accurately with the Mahadevan method for all systems, including an intrinsically amorphous PLA.